Pharmacokinetics of new testosterone transdermal therapeutic systems in gonadotropin-releasing hormone antagonist-suppressed normal men

In a phase I single-center, open, randomized pilot study with a three-way c ross-over design the pharmacokinetics of three testosterone-containing tran sdermal therapeutic systems were evaluated in healthy male volunteers. Test osterone TTS HEXAL type 1 and 2 are nonscrotal membrane patches differing i n the kind of adhesive used. 6 subjects were treated with low dose Testoste rone TTS type 1, high dose Testosterone TTS type I and low dose Testosteron e TTS type 2. To eliminate the influence of endogenous serum testosterone, the endogenous testosterone secretion was suppressed by the GnRH antagonist cetrorelix. In all subjects under GnRH antagonist treatment a marked suppr ession of LH, FSH, testosterone, DHT and estradiol was observed. Physiologi c testosterone levels were achieved during the 24-hour-application period. Maximal serum levels were reached after 4 hours with both TTS systems. Both systems appear suited for further testing because both enable a physiologi cal circadian profile to be achieved. GnRH-antagonist pretreatment is a use ful model to evaluate the effect of exogenous testosterone in clinical stud ies, when, due to fluctuations in endogenous hormone levels, an estimation of the proportion of exogenous steroid is not possible.